Do Acoustic Panels Work?
Updated
Yes, acoustic panels work on echo: by the standard Sabine formula, eight 2 by 4 ft panels of 2 in. fiberglass cut the echo time of a bare 12 by 15 ft room from about 1.8 seconds to 0.7. Do acoustic panels work on noise from next door? No. That takes blocking, and blocking is a different job.
Example: A 12 by 15 ft room with an 8 ft ceiling holds 1,440 cu ft and has 792 sq ft of surfaces. At drywall's NRC 0.05 (Johns Manville (opens in a new tab)), absorption is 792 × 0.05 = 39.6, and echo time is 0.049 × 1,440 ÷ 39.6 = 1.8 s (Sabine formula, University of Illinois (opens in a new tab)). Cover 64 sq ft with 2 in. Owens Corning 703 (opens in a new tab) panels (NRC 1.00): absorption goes to 728 × 0.05 + 64 = 100.4, and echo time drops to 0.7 s.
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Echo time estimator
See how panels change how long a clap rings in an empty room.
Echo time (RT60) = 0.049 × room volume in cu ft ÷ total absorption in sabins (Sabine formula, University of Illinois (opens in a new tab)). In a bare 12 by 15 ft room with an 8 ft ceiling, every surface at drywall's 0.05 gives 792 × 0.05 = 39.6 sabins and an echo time of 1.8 s. Eight 2 by 4 ft panels of 2 in. fiberglass (NRC 1.00) bring it to 0.7 s; six bring it to 0.8 s.
Based on: Do Acoustic Panels Work?, What Do Acoustic Panels Do?
Two catches change the count. Furniture, rugs and curtains already lower the starting number, so a lived-in room needs fewer panels. And thin panels don't do much for bass: 2 in. of 703 absorbs 0.15 of the sound at 125 Hz, against 0.56 for 4 in.
What panels can't do is block sound through a wall, because a 2 in. panel weighs only 0.5 lb/sq ft. Acoustic panels vs soundproofing puts the two jobs side by side, do soundproof panels work sorts common problems into echo and noise, and the soundproof panels guide matches panel types to rooms. There are more answers in the soundproof panels FAQ.